This invention relates to electro-mechanical measurement and control systems. These systems measure physical parameters as temperature, pressure, position, velocity, or acceleration and use these measurements to indicate the measured parameter or to control machinery or processes. Historically, the devices used to perform the measurement function have exploited a variable relationship between some electrical phenomenon as capacitance, resistance, inductance and the physical parameter to be measured or, have used the interplay between a magnetic field and an electrical phenomenon. The devices have had continuity of output that is analogue in nature and lends itself to use with analogue systems. Analog sensing devices have been developed to a high state of utility.
As digital electronic information processing has improved, the search has developed for digital signal sources to indicate physical parameters for measurement and system control. Interfaces have been developed that allow analogue sensing devices to be used with digital controls. However, there remains a need for sensors that have digital output and integrate seamlessly with digital equipment.
When high-speed position measurement is made with conventional devices that employ a magnetic field there is a delay between the actual position and the indicated position. This delay is referred as measurement hysteresis. This measurement hysteresis is undesirable in practice. There is a need for measurement devices with lower measurement hysteresis.